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Archive | August 2017

With the price of 100G QSFP28 optics and CFP form factors (CFP module/CFP2/CFP4) dropping down in 2017, 100G technology is becoming more and more popular among data center managers and IT pros in order to cope with the ever-lasting bandwidth needs. However, 100G is not the finish line. CFP multimode source agreement (MSA) demonstrated CFP8 (16X 25 Gb/s) form factor for 400 Gigabit Ethernet at OFC 2017. Although CFP8 module is still in development, it is assured to be popular in the near future. Therefore, this article will have a clearer introduction to 400G CFP8 PAM4 and NRZ modules, and compare with the former CFP modules and 400G CDFP.

Introduction to 400GbE CFP8 Modules

CFP8 module is the latest developing CFP from factor version, which supports eight times and four times the bandwidth density of CFP and CFP2 form factors, respectively. The CFP8 interface supports up to 16 different lanes in each direction with nominal signaling rates of 25Gb/s or 26Gb/s per lane, and either NRZ or PAM4 signaling. As the above image shows, CFP8 is approximately the size of a CFP2 optics. This interface has been generally specified to allow for 16 x 25 Gb/s and 8 x 50 Gb/s mode.

The PAM4 stands for pulse amplitude modulation with four levels. Instead of driving the laser to generate one of the two output amplitudes, like NRZ, PAM4 technology generates four different amplitude levels, meaning a network based on PAM-4 can send twice as much data as an NRZ version.

CFP8 400GBASE-SR16 with NRZ Technology

CFP8 400GBASE-SR16 modules focus on non-return to zero (NRZ) signal modulation Scheme. To use an analogy, it means you’re sending signals in the most simple format: “light on” and “light off.” A ‘1” is transmitted as pulse of light whereas ‘0” is no light output. Based on the currently available fast VCSEL light sources only achieving data rates of 25G, sixteen channels must transmit in parallel to create a 400G data stream.

Due to the design simplicity NRZ, the modulation format of choice for all data rates up to 25Gb/s. 400GBASE-SR16 CFP8 transceivers requires 16 fiber pairs to support a total of 400Gb/s with MPO multimode cables.

What’s New With CFP8 Module?

A CFP8 module is a hot pluggable module. Compared with the former modules, the control and status reporting functions between a host and a CFP8 module use non-data control and status reporting pins on the 124-pin connector. There are three Hardware Control pins, two Hardware Alarm pins, and four pins dedicated to the MDIO interface.

Compared to CFP2/CFP4 MSA Optics

CFP8 is the proposed CFP8 from factor by MSA member companies. It maintains the large size of CFP form factor (nearly the size of CFP2, larger than CFP4 MSA modules), but supports 4x100G i.e. 4x the CFP2. Besides this, CFP8 uses less power than the former CFP form factor modules. There are 400GBASE-SR16 for parallel MMF 16x25G NRZ, and 400GBase-FR8/LR8 duplex SMF 8x50G PAM4 WDM.

CFP8 Vs. CDFP

CFP8 is not the first released 16x25G= 400G modules, but CDFP. 400G CDFP module (CD=400 in Latin), is the four generation CFP form factor. Providing a high level of integration, performance and long-term reliability, the CDFP 400 Gbps interface is available in short- and long-body versions. The specifications are compatible for use with direct attach cables, active optical cables, and connectorized optical modules. The CDFP module will support:

5 meter direct attach cables

100 meter multimode fiber

500 meter parallel single‐mode fiber

2 kilometers of duplex single‐mode fiber

The compact modules are well suited for low power applications using copper, VCSEL or silicon photonics based technology. They also targeted InfiniBand EDR hydra cables and 128GFC applications but so far little market segment pick up. Though relatively new with 2014 and 2015 rev releases, CDFP may be short lived due to the smaller more efficient developing set of CFP8 solutions.

Latest Trend With 400 Gb/s in the Industry

While 400 GbE standard is still a few years away, the need for 400 Gb/s interfaces is here today. The CDFP form factor is already being used in proprietary interfaces to interconnect high performance servers and will soon be used to interconnect switch and router chassis. 400G CFP8 FR8/LR8 PAM4 and 400GBASE-SR16 modules had been displayed at OFC 2017. Finisar, Fujitsu, and oclaro, etc MSA member enterprises will introduce low profile 400G modules in a short period.

These proprietary chassis interconnects have always been massively parallel and will continue because they provide the massive bandwidth needed to interconnect equipment so that multiple chassis perform as one big chassis. While 16 lanes is a fairly wide interface, multiple applications need the maximum amount of bandwidth that can only be provided by many parallel lanes running at the fastest speed available. It seem that CFP8 with the same 16 MPO connectors has much potential than CDFP modules. FS.COM offers a large stock MSA-compliant optical transceivers, including 100G CFP/CFP2/CFP4 MSA, CXP, and QSFP28 transceiver modules. We will keep in path with the informative world, and provide the best services & telecom products to all of our customers.

Optical amplifier, with the introduction in 1990s, conquered the regenerator technology and opened doors to the WDM technology. It is mainly used to amplify an optical signal directly, without the need to first convert it to an electrical signal. There are many types of optical amplifiers, namely Raman amplifiers, erbium doped-fiber amplifiers (EDFAs), and semiconductor optical amplifier (SOA). This article will make a clearer introduction to SOA amplifier, and analyze its advantages and disadvantages.

The Basics of Semiconductor Optical Amplifier (SOA)

SOA optical amplifiers use the semiconductor as the gain medium, which are designed to be used in general applications to increase optical launch power to compensate for loss of other optical devices. Semiconductor optical amplifiers are often adopted in telecommunication systems in the form of fiber-pigtailed components, operating at signal wavelengths between 0.85 µm and 1.6 µm and generating gains of up to 30 dB. Semiconductor optical amplifier, available in 1310nm, 1400nm, 1500nm, 1600nm wavelength, can be used with singlemode or polarization maintaining fiber input/output.

Key Points of SOA Amplifier

1310 nm, 1400 nm, 1550 nm and 1610 nm wavelength selectable

High fiber-to-fiber gain of 20 dB

Up to 16 dBm output

1 MHz with 10 ns pulse width (optional)

PM Panda fiber input/output (optional)

Similar to lasers, but with non-reflecting ends and broad wavelength emission

Incoming optical signal stimulates emission of light at its own wavelength

Process continues through cavity to amplify signal

Working principle of SOA amplifier

The basic working principle of a SOA is the same as a semiconductor laser but without feedback. SOAs amplify incident light through simulated emission. When the light traveling through the active region, it causes these electrons to lose energy in the form of photons and get back to the ground state. Those stimulated photons have the same wavelength as the optical signal, thus amplifying the optical signal.

SOA Over EFDA in DWDM Networks

As the solution below, 120km Metro Networks by Using an SOA amplifier. You may wonder why not use EDFA in the above networks.

Theoretically, SOA optical amplifiers are not comparable with EDFA in the terms of performance. The noise figure of SOA optical amplifier is typically higher, the gain bandwidth can be similar, SOAs exhibit much stronger nonlinear distortions in the form of self-phase modulation and four-wave mixing. Yet, the semiconductor optical amplifier is of small size and electrical pumped, which is often less expensive than EDFA. Additionally, SOA can be run with a low power laser.

How to Choose SOA Optical Amplifier?

When selecting SOA amplifier, you have to check the every detailed parameter in the product data sheet. But, seriously, do you understand it? No, please read the following part.

The key parameters used to characterize a SOA amplifier are gain, gain bandwidth, saturation output power and noise.

Gain is the factor by which the input signal is amplified and is measured as the ratio of output power to input power (in dB). A higher gain results in higher output optical signal.

Gain bandwidth defines the range of bandwidth where the amplification functions. A wide gain bandwidth is desirable to amplify a wide range of signal wavelengths.

Saturation output power is the maximum output power attainable after amplification beyond which no amplification is reached. It is important that the SOA has a high power saturation level to remain in the linear working region and to have higher dynamic range.

Noise defines the undesired signal within the signal bandwidth which arises due to physical processing in the amplifier. A parameter called noise figure is used to measure the impact of noise which is typically around 5dB.

Conclusion

SOA amplifier is the economic, high-performance solution for long-hual WDM networks. SOA amplifier, due to its features, can be used in Booster and in-line amplification, optical network, general purpose test and measurement and fiber sensing. However, it also has its limit. In semiconductor optical amplifiers, electron-hole recombination occurs which will affect the performance of the whole line. FS offers EDFA, SOA, Raman optical amplifiers of excellent quality and price. For more detailed information, please feel free to contact us.

OM5 multimode fiber, as the advanced version of the old OM4 fiber, is thought to be the future of multimode cabling. It is the Wideband multimode fiber (WBMMF) that can support wavelengths between 850nm and 953nm. It is also designed to support the short wavelength division multiplexing (SWDM)—one of the new technology for 40G/100G connection. However, will it be the ideal transmission medium for 40GbE/100GbE cabling solution?

How OM5 Fiber Developed

Over the past thirty years, multimode fiber has been evolved from OM1 to OM5 multimode fiber. OM1 and OM2 fiber, released at the end of 20th century, are the legacy 125µm multimode fiber that are working fine in 10Mb/s, 100Mb/s and 1000Mb/s cabling solution. However, with the high speed data rate like 10Gb/s, 40Gb/s, 100Gb/s and beyond coming into our life, multimode cabling (OM1 and OM2 ) with LEDs can not meet the requirement. The laser-optimized OM3 and OM4 has been developed subsequently. OM4 fiber cable, with the internal construction, possess higher modal bandwidth than OM3 fiber, which is commonly used fiber medium for 40G/100G connection.

But there is a problem. In a 40G layout, fiber optic technicians have to use one MTP fiber and 4 OM4 duplex fibers (total 8 fibers), which is obvious not preferable for high-density cabling networks. So here comes the OM5 fiber. By utilizing SWDM technology, it can greatly reduce fiber count into 2 fibers (4×10G) in 40G networks, 2 fibers (4×25G) in 100G links. OM5 is the lime green multimode fiber, displayed as follows.

OM5 Fiber for 40G/100G SWDM4 Cabling Solution

Reduce fiber count for 40G/100G connection—OM5 fiber as the advanced version of OM3/OM4 fiber, is backward compatible with OM3 and OM4 fiber cabling. And with the SWDM technology, this fiber can only use two OM5 fibers and 40/100G SWDM4 transceivers in 40G and 100G SWDM4 cabling.

Longer-transmission distance—OM5 is designed and specified to support at least four WDM channels at a minimum speed of 28Gbps per channel through the 850-953 window. Compared to OM4 fiber cable, it is specified only to work at the 850 nm window. OM5 multimode fiber delivers higher value to network owners for distances up to 440m (for data rates up to 40Gbps), and allows for smooth migration to 400Gbps for distances up to 150m. While OM4 fiber cover the distance of 350m, 100m over 40G/100G respectively.

Easy management & installation—in 40G/100G network, multimode connectivity together with MTP/MPO systems makes for a more user-friendly solution for data centers as well as building and campus backbones, especially in cable installation, troubleshooting, cleaning, and overall maintenance.

FS OM5 Cable Solution

FS offer Lime green OM5 fibers. All our OM5 fiber cables are guaranteed by End Face Geometry Test, Continuity Test, and 3D interferometry Test to be high quality. Available in LC, SC, FC, ST, etc. Connectors, and the cable length of OM5 fiber can be provided from less than 1 meter to more than 100 meters, which will well meet the needs for 400m transmission of 40G SWDM4 QSFP+ module and 100m transmission of 100G SWDM4 QSFP28 module, as well as the links on the same rack or row.

Not only the OM1/OM2/OM3/OM4/OM5 multimode fibers are provided at FS.COM, but fiber optic cables like singlemode fibers (OS1/OS2) , Twinax copper cables are also offered. For more information about the cost-effective fiber patch cables, Please feel free to contact us via http://www.fs.com.